Actuator and material for the actuator

ABSTRACT

A material for an actuator is provided which is reduced in weight, can be micro-miniaturized and can be used stably in a gas phase such as in atmospheric air safely, and an actuator using the material is provided. The material used for the actuator comprises a material formed by mixing fine conductive particles with a polymer material having a large absolute value of thermal expansion coefficient.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2005-146337 filed on May 19, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an actuator module reduced in weightand capable of causing deformation such as expansion and contraction,bending, or the like repetitively by electric signals, and a materialused therefor.

2. Description of the Related Art

Medical or nursing fields require safety actuators that can bemicro-miniaturized and reduced in weight and that are flexible andoperated at a low driving voltage for the application use of activecatheters, endoscopes, rehabilitation aids, powered suits, artificialorgans, etc. Further, paper displays and portable haptic devices forwhich a new demand will be expected in the future require actuatorscapable of attaining complicate movements in a small space in additionto the properties described above. As described above, not onlyactuators that can generate large stresses and high-speed response andcan be controlled with high accuracy as usual but also actuators thatcan be micro-miniaturized and reduced in weight, and that is flexibleand safe attaching to the boty(low driving voltage) will be necessary inthe future.

For the actuators that can be micro-miniaturized, actuators in which amaterial per se can deform repetitively by electric signals are moresuitable than those requiring assembling of parts such as anelectromagnetic motor used usually. Actuators well-known at present inwhich the material per se deforms repetitively include a piezo actuatorutilizing the piezo effect of ferroelectrics and an SMA actuatorutilizing the phase transition of a shape-memory alloy (SMA). However,they have good and bad points in view of the driving voltage, theweight, and the durability.

As the actuator using the material that is deformed by electric signals,several kinds of actuators utilizing organic materials that deform byelectric signals have been proposed in recent years, separately from theexistent actuators described above. Since such actuators use organicmaterials, they have an advantage of reduced weight. They include,specifically, polymer actuators represented typically, for example, by aconductive polymer actuator using a conductive polymer such aspolyaniline or polypyrrole for the material (Patent Document 1: JP-A No.02-20586), an tonically conductive polymer actuator using an ionicallyconducting polymer as the material (Patent Document 2: JP-A No.06-6991), a fine conductive particles mixed ionic polymer actuator inwhich fine conductive particles are bound with an ionic conductivepolymer (Non-Patent Document 1: “Expanding actuator using ionicconductive polymer, by Masayoshi Ishibashi, Midori Kato, in 53th AnnualMeeting of the Society of Polymer Science, Japan, 2004, IPA155), anactuator utilizing thermal deformation upon molecular desorption ofconductive polymer (Patent Document 3: JP No. 3131180) and an actuatorof using a material formed by mixing fine conductive particles to ashape memory resin (Patent Document 4: JP-A No. 02-242847, PatentDocument 5: JP-A No. 02-155955).

SUMMARY OF THE INVENTION

The actuator utilizing the organic material that deforms depending onelectric signals is reduced in the weight and can be easilymicro-miniaturized; however, it involves several problems in view ofoperating circumstance and controllability. For example, most of polymeractuators conduct expanding and contracting operation only in anelectrolyte solution by applying a voltage to counter electrodesdisposed in the same electrolyte solution. Accordingly, the applicationuse of the actuator is restricted to the inside of a body or in seawater and, to operate the actuator in a gas phase such as in atmosphericair, it is necessary to add a component such as packaging.

On the other hand, an actuator that utilizes the deformation bymolecular desorption of a conductive polymer can operate in a gas phase.Since deforming by desorption of molecules such as of water, however,the actuator involves a problem in that the operation greatly depends onthe surrounding circumstance such as humidity and the response is slowas well. For the material providing a shape memory resin with electricconductivity, since the deformation of the material is basicallyirreversible and does not repeat deformation in accordance with inputelectric signals, some or other devices are necessary for obtaining theoperation as the actuator.

It is an object of the present invention to provide an actuator that canbe used stably in a gas phase such as in air with safety, and can bemicro-miniaturized, controlled satisfactorily, and reduced in weight.

Since a polymer material of high thermal expansion coefficient is aninsulator, control of the temperature by heating under electric supplyis difficult. In addition, since the material such as a metal of highelectric conductivity has small thermal expansion coefficient, it isdifficult to obtain large expansion and contraction within a practicalrange of temperature. In the invention, to attain the forgoing object,an actuator uses a material of high thermal expansion coefficient andhigh electric conductivity. The actuator according to the inventionconducts self heat generation by electric supply to the actuatormaterial and conducts expanding and contracting operation by utilizingthe deformation of the material due to large thermal expansion andcontraction caused by the change of the temperature.

The invention can provide a light weight and flexible actuator that canbe used stably in a gas phase such as in air with safety and can beminiaturized, and that has good controllability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram schematically showing the state of an actuatormaterial before voltage is applied thereto;

FIG. 1B is a diagram schematically showing the state of the actuatormaterial when the voltage is applied thereto;

FIGS. 2A and 2B are diagrams for explaining the basic operation of anactuator according to the invention using deformation of the actuatormaterial as described for FIG. 1 by heating under electric supply;

FIG. 3 is a graph showing the relationship between the strain of anactuator film 1 and electric energy input to the film;

FIGS. 4A to 4D are conceptional diagrams showing the steps of amanufacturing method of an actuator film of Embodiment 1;

FIG. 5 is a perspective view of a substrate used for molding theactuator film by way of example;

FIGS. 6A and 6B are cross sectional views showing the concept of anactuator module structure of Embodiment 2 in which FIG. 6A illustratesthe state of the actuator module before voltage is applied thereto andFIG. 6B illustrates the state of the actuator module when the voltage isapplied thereto;

FIGS. 7A to 7C are conceptional views showing the form of an actuatormodule structure utilizing the V-shaped structure in which FIG. 7A is aperspective view for the outer profile of an actuator module using theV-structure as viewed obliquely from above, FIG. 7B is a cross-sectionalview of an actuator module showing the state of lowering a pin in a casewhere voltage is not applied to the actuator module, and FIG. 7C is across sectional view of the actuator module showing the state ofexpanding the actuator film by applying a voltage to the actuator moduleto move the pin upward;

FIGS. 8A and 8B are conceptional upper plan views showing an actuatormatrix using the actuator module shown in FIG. 7;

FIGS. 9A is a conceptional perspective view showing the state of aBraille display device 90 using the actuator module described in FIG. 6for Embodiment 2;

FIG. 9B is a conceptional perspective view of a Braille display systemusing the Braille display device 90;

FIG. 10A is a conceptional upper plan view of a Braille display device100 using the actuator module 70 described in FIG. 7 for Embodiment 2;

FIG. 10B is a conceptional view of the Braille display system 101 usingthe Braille display device 100;

FIGS. 11A and 11B are explanatory upper views for the actuator module inwhich expanding and contracting operation of the actuator film describedfor Embodiment 1 is converted to bending operation in which FIG. 11A isa schematic perspective view illustrating the state before applicationof voltage to the actuator module 110 and FIG. 11B is a schematicperspective view for the state of applying the voltage to the actuatormodule 110;

FIG. 12A is a schematic plan view illustrating the state of a conveyingdevice 120 utilizing a plurality of bending actuator modules 110described in Embodiment 4 and a convey system including a controlcircuit for operating the conveying device 120;

FIG. 12B is a perspective view of the conveying device 120 as viewedfrom obliquely above;

FIG. 13A illustrates a state where an electric current is not suppliedto any of actuator columns of the conveying devices, FIG. 13Billustrates the state where an electric current is supplied to anactuator column 128 b and an actuator column 128 d, FIG. 13C illustratesthe state where an electric current is supplied also to an actuatorcolumn 128 a and an actuator column 128 c from the state in FIG. 13B,FIG. 13D illustrates the state where the electric supply is interruptedto the actuator column 128 b and the actuator column 128 d, and FIG. 13Eillustrates the state just after electric supply is interrupted to allthe actuator columns;

FIGS. 14A and 14B are diagrams showing other application mode of thebending actuator module shown in Embodiment 4;

FIGS. 15A and 15B are conceptional diagrams showing an optical switchingdevice 150 for switching the optical channel of an optical fiber asother application embodiment of the actuator module of the V-shapestructure shown in Embodiment 2;

FIG. 16A is a schematic view illustrating a longitudinal cross sectionalstructure of a flexible tube 160 such as a catheter, as a medical tube;

FIG. 16B is a schematic view for a cross sectional structure as viewedin the direction of arrows along X-X′ in FIG. 16A;

FIG. 16C is a schematic view of a cross sectional structure showing thestate of bending a bend portion 161 in the flexible tube 160;

FIG. 16D is a conceptional view of a medical catheter system using theflexible tube 160;

FIG. 17A is a schematic view of a longitudinal cross sectional structureof a flexible tube 170 such as a catheter, as a medical tube; and

FIG. 17B is a schematic view of a cross sectional structure as viewed inthe direction of arrows along X-X′ in FIG. 17A.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the invention, since a material formed by mixing fineconductive particles with a polymer material having high thermalexpansion coefficient is used for an actuator, electric conductivity isapplied to the polymer material insulative by nature and self heatgeneration by electric supply and large deformation caused thereby canbe enabled. Repetitive expanding and contracting operation is possibleby conducting deformation at a temperature within a range of not causingplastic deformation under loading.

Conditions for obtaining a large displacement in the actuator accordingto the invention are to be described. The actuator of the inventionutilizes. the deformation by thermal expansion. Generally, the amount ofdeformation ΔL by thermal expansion of an object with a length L is inproportion with the temperature change ΔT and the proportional constantis a coefficient of linear thermal expansion α. That is, they are in therelation shown by equation (1):ΔL=α×ΔT×L   (1)

In the actuator of the invention, the temperature of the actuatorchanges depending on the Joule heat generated by electric supply.Generally when a certain voltage is applied to a substance, assuming theelectric resistance R is constant during application of the voltage, theJoule heat E generated during the time t is expressed as in equation(2):E=V ² /R×t   (2)in which the resistance R is represented by using the electricconductivity κ as in equation (3):R=1/κ×L/S   (3)in which S is a cross sectional area of the substance. Accordingly,based on equations (2) and (3), the Joule heat E generated by theapplication of the voltage is as shown in equation (4):E=(κ×S×V ² ×t)/L   (4)

On the other hand, the relationship between the Joule heat E and thetemperature increase ΔT of the substance caused thereby can be writtenas in equation (5) assuming the specific heat of the substance as “c”,the specific gravity as σ, and the energy loss caused by radiation orheat conduction as E′.E−E′=c×σ×S×L×ΔT   (5)

Accordingly, based on equations (5) and (4), the temperature increase ΔTcan be written as in equation (6).ΔT=(κ×V ² ×t−E′×L/S)/(c×σ×L ²)   (6)

Based on equations (6) and (1), the deformation amount ΔL is as shown inequation (7).ΔL=α×(κ×V ² ×t−E′×L/S)/(c×σ×L)   (7)

Accordingly, it can be seen that the deformation amount ΔL increases ina material having a large thermal expansion coefficient α, a highelectric conductivity κ and a small specific gravity σ.

Table 1 shows typical values for the material constants with respect tometal, ceramic, polymer material, and the material of the invention.Further, Table 1 also shows the tensile strength as the mechanicalcharacteristic of the material. In a case of an actuator of the typewhere the material per se deforms, the force exceeding the limit atwhich the material per se is broken can not be outputted. That is, themaximum force generated as the actuator depends on the tensile strengthof the material. TABLE 1 Coefficient of linear thermal Electric Tensileexpansion α conductivity Specific strength (×10⁻⁵/K) κ (S/cm) gravity σ(MPa) Metal 1-2 10⁵-10⁶  2-20  100-1000 Ceramic 0.2-0.6 10⁻¹⁴-10⁻¹¹ 330-50 Polymer  1-20 10⁻¹⁵-10⁻⁸  0.9-1.5  4-100 material Invention  1-10010⁻¹-10⁻³ 0.5-5    0.3-200

Since the material of the invention mainly comprises a polymer material,the expansion coefficient is large and the specific gravity is small.Further, since the material is mixed with the fine conductive particles,the electric conductivity is high to some extent. Accordingly, apractical actuator can be provided which has large deformation byheating under electric supply. Further, since it has not so high theelectric conductivity as metal, the material also has a merit of notrequiring large current for heating without using a super thin film. Amethod of mixing fine particles with the polymer material is oftenpracticed with an aim of improving the mechanical strength of thepolymer material. Therefore, also the tensile strength of the materialaccording to the invention is larger than that of the polymer material.

The present invention is to be described by way of examples withreference to the drawings.

EMBODIMENT 1

In Embodiment 1, the concept of the basic operation of an actuatoraccording to the invention and a manufacturing method thereof are to bedescribed. At first, a description is to be made of the deformation ofan actuator material when a voltage is applied to the actuator materialconstituting the actuator of the invention.

FIG. 1A schematically shows the state of an actuator material beforevoltage is applied thereto and FIG. 1B schematically shows the state ofthe actuator material when the voltage is applied. In the figures, areshown a polymer material 2 of large thermal expansion coefficient, fineconductive particles 3, and an actuator material 10 in which the fineconductive particles 3 are dispersed in the polymer material. There arealso shown a power source 4 and a switch 5. Current can be supplied orstopped to the polymer material 10 by turning the switch 5 on or off.When a voltage of the power source 4 is applied to the actuator material10 with the switch 5 being turned on, the temperature of the actuatormaterial 10 increases by the Joule heat, and isometric deformation iscaused in the actuator material 10 in accordance with the thermalexpansion coefficient (FIG. 1B). On the other hand, when the switch 5 isturned off, electric supply to the actuator material 10 is stopped, thetemperature is lowered and the actuator material 10 resumes an originalshape (FIG. 1A). It will be apparent that the shape change can beconducted in a gas phase such as in atmospheric air. The actuator of theinvention conducts expanding and contracting operation by utilizing thephenomenon.

Specifically, fine carbon particles with a size of about 40 nm were usedas the fine conductive particles 3 and a perfluorosulfonicacid-copolymer was used as the polymer material 2, and they were mixedat a mixing ratio of about 1:5 by weight ratio to form the actuatormaterial 10. In this case, when the application voltage was controlledto optimize the temperature of the actuator material 10 during electricsupply, a strain of about 2% at the maximum was obtained. The strain isa quantity represented by ΔL/L assuming the entire length of theactuator before voltage application as L and the expansion of theactuator upon voltage application as ΔL.

The perfluorosulfonic acid-copolymer used in the polymer material 2 is afluoro polymer, which is a material of high thermal expansioncoefficient excellent in the heat resistance. By mixing and dispersingthe fine carbon particles with the material, an actuator material 10 ofhigh thermal expansion coefficient and high electric conductivity can beformed. The actuator material 10 of Embodiment 1 has a coefficient oflinear thermal expansion of 0.0001/K at 100° C., an electricconductivity of 1 siemens/cm, and a glass transition temperature of 230°C. Since the strain of the actuator material 10 by voltage applicationis about 2%, it can be estimated that the temperature of the actuatormaterial 10 increases to about 220° C. by the voltage application.

In a case of conducting the deformation of the actuator material byheating under electric supply as described with reference to FIGS. 1Aand 1B in a state of applying a load such as a weight on the actuatormaterial, the load can be moved reversibly within a certain range of theload, so that the material can be used as the actuator.

FIGS. 2A and 2B are views for explaining the basic operation of theactuator according to the invention utilizing the deformation by heatingunder electric supply of the actuator material as described in FIG. 1.FIG. 2A shows a state before application of the voltage while applyingonly a load such as a weight to an actuator film 1, and FIG. 2B shows astate of applying the voltage to the actuator film 1 while applying theload. The actuator film 1 is formed as a film shape being longer on oneside of the actuator material 10, so that the deformation by the voltageapplication is small and negligible, compared with that in thelongitudinal direction, in the portion other than the longitudinaldirection of the film. An electrode 6 and an electrode 7 for applyingvoltage are disposed at both longitudinal ends of the actuator film 1,to which an external power source 4 and a switch 5 are connected inseries therewith. Further, one end of the actuator film 1 is fixed to awall or the like and the other end thereof is subjected to a load 8 inthe direction where the actuator film 1 is pulled (FIG. 2A). In thiscase, the magnitude of the load 8 should not exceed the tensile strengthof the actuator film 1. As with the case of FIG. 1B, when the switch 5is turned on in this state and a voltage from the power source 4 isapplied to the actuator film 1, the actuator film 1 expands thermally bythe temperature increase by heating under electric supply, that is, thefilm elongates (FIG. 2B). When the switch 5 is turned off in this state,the actuator film 1 lowers in temperature and contracts again (FIG. 2A).In this case, along with expansion and contraction of the actuator film1, the load 8 moves vertically. That is, the expanding and contractingoperation of the actuator film 1 can be taken out as work of thevertical motion. In a case of restricting the temperature upon electricsupply to the actuator film 1 to a value lower than the glass transitiontemperature, the expanding and contracting operation of the actuatorfilm 1, that is, the vertical motion of the load by heating underelectric supply can be repeated reversibly.

In a case of using the actuator film 1 measuring 1 cm in length, 2 mm inwidth, and 120 μm in thickness, attaching a weight of 50 g as the load 8thereto and applying thereto a rectangular wave voltage at an amplitudeof 22 V and at a frequency of 1 Hz, the strain of the actuator film 1per 1 pulse was about 2%. That is, the load 8 of 50 g weight could bemoved vertically for about 200 μm at a frequency of 1 Hz. In thisexample, the force generated by the actuator film 1 is about 2 MPa. Theactuator material of Embodiment 1 can generate a force of about 3 MPa atthe greatest.

Further, the actuator film 1 of Embodiment 1 conducts expanding andcontracting operation in accordance with the frequency also when arectangular voltage at 10 Hz was applied thereto. Further, when it wascaused to actuate the expanding and contracting operation for 100,000cycles (repeating the state of FIGS. 2A and 2B), the value of the strainwas not changed from the initial state and the actuator film wasoperated stably.

FIG. 3 shows the relationship between the strain of the actuator film 1per 1 pulse and the electric energy input to the film upon applicationof a rectangular wave voltage with an amplitude of 15 V and at afrequency of 1 Hz. It can be seen that a proportional relation isestablished between the strain of the actuator film 1 and the electricenergy input to the film. Accordingly, the magnitude of the expansionand contraction of the actuator film 1 can be easily controlledelectrically by controlling the input electric energy. While a DC powersource was used as the power source in this case, since the strain ofthe actuator film 1 is in proportion to the input electric energy, itcan be controlled in the same manner by the control for the inputelectric energy also by using an AC power source. In any of the cases,while it is the simplest to conduct control by the voltage applied tothe actuator film, it will be apparent that current control is alsopossible.

Further, the electric resistance of the material according to theinvention is a resistance of the fine conductive particles mixed in thepolymer and the resistance between the fine particles. When the actuatorfilm 1 deforms, therefore, the resistance between the fine particleschanges and, as a result, the resistance of the actuator film alsochanges. By monitoring the same, the deformation of the actuator film 1can be estimated. Accordingly, the deformation can be controlledaccurately by applying feed back to the application voltage by using theresistance value.

When a constant voltage continuously applied to the actuator film 1, thedeformation amount of the film is converged to a predetermined valueunless the temperature of the film exceeds the glass transitiontemperature or the melting point or decomposes point of the material forthe actuator film. This is because the input electric energy and theenergy emitted by radiation, conduction, convection, etc. are in abalanced state. Once the balanced state is reached, the deformationamount can be maintained constant.

In a case where the polymer material 2 used for the actuator film 1 hasa polymeric hygroscopicity, when the film is left at room temperature,it contains surrounding humidity to swell somewhat more greatly comparedwith the dried state. However, by always supplying a low current to thefilm, the temperature of the film can be elevated to evaporate the watercontent and keep the film in a dried state irrespective of thesurrounding humidity. By using the method described above, thedeformation amount of the actuator film can be controlled accurately notdepending on the surrounding humidity even in a case of usinghygroscopic material.

As also described previously, in a case where the electric energy inputto the actuator film 1 is large and the temperature of the film exceedsthe glass transition temperature of the material for the actuator film1, the mechanical characteristic of the film is remarkably deteriorated.That is, the tensile strength is lowered to form an extremely soft stateand the film causes plastic deformation even by a small load and no moreresumes the original shape. In such a state, it can not operate as theactuator. Since the amount of deformation by the thermal expansion islarger as the temperature difference is larger, the maximum deformationamount in the invention is restricted by the glass transitiontemperature of the actuator film 1 as a determinative factor. Since theactuator film 1 is a composite material of the polymer material 2 andthe fine conductive particles 3, the glass transition temperature of thefilm depends on the glass transition temperature of the polymer material2. Accordingly, when a material of high glass transition temperature isused for the polymer material 2, the workable temperature range isextended accordingly and, consequently, the deformation amount of theactuator film 1 can also be made larger.

However, depending on the type of the polymer material such as acrystalline polymer, the polymer material may not have a glasstransition point. In this case, it is necessary to control the inputenergy so that the operation is not conducted at a temperature exceedingthe melting point or the decomposition point of the material. Also inthis case, the melting point or the decomposition point of the materialfor the actuator film 1 depends on the melting point or thedecomposition point of the polymer material 2 forming the actuator film.Therefore, the workable temperature range can be extended, that is, thedeformation amount of the actuator can be made larger by using amaterial of high melting point or decomposition point as the polymermaterial 2.

Further, to greatly deform the actuator film 1 of the invention, it isnecessary that not only the heat resistance but also the expansioncoefficient are high. That is, polymer materials of high softening pointand high thermal expansion coefficient are suitable to the polymermaterial 2 used in the actuator film 1. The polymer materials describedabove include, in addition to the perfluorosulfonic acid-copolymer usedfor the polymer material 2 in Embodiment 1,acrylonitrile-butadiene-styrene copolymer, polymethacrylate ester suchas acrylic resin, polyethylene terephthalate, polyamide,polyoxymethylene, polytetrafluoroethylene, polystyrene, polycarbonate,and polyalkenes such as polycyclohexylethylene, polyacrylic acid, andpolymethacrylic acid, etc. They can be used as the polymer materialconstituting the actuator film. The coefficient of linear thermalexpansion of the polymer materials described above is generally from0.00001/K to 0.0002/K. Accordingly, the coefficient of linear thermalexpansion of the actuator film using them as the constituent material isalso 0.00001/K or more. On the contrary, in a case where the coefficientof linear thermal expansion is excessively large, since the deformationis large and the burden on the material increases, the coefficient oflinear thermal expansion is appropriately at about 0.001/K or less.

While fine carbon particles with a diameter of 40 nm are used for thefine conductive particles 3 of the actuator film 1 in Embodiment 1, fineconductive carbon particles of a larger size, carbon nanotubes, finemetal particles such as of gold, silver, platinum, copper, and nickel,or mixtures thereof can also be used. The electric conductivity of theactuator film can be changed by changing the kind of the fine conductiveparticles and the mixing ratio with the polymer material. In a casewhere the electric conductivity is low, a high voltage is necessary fordriving. On the other hand, in a case where the electric conductivity isexcessively high, supply of large current is required and a usual powersource can not be used. The practical value of the electric conductivityis from 0.1 to 1000 siemens/cm.

Generally, when fine particles are mixed with the polymer material, themechanical strength of the composite material increases. Increase of thestrength by about twice can be expected also depending on the type andthe amount of the material to be mixed. The tensile strength of theactuator film of the invention as the composite material has a tensilestrength about twice the polymer material as the constituent material,that is, about 200 MPa at the maximum. On the other hand, as describedpreviously, the maximum stress generated from the actuator depends onthe tensile strength of the material. Accordingly, a material ofexcessively low tensile strength does not work as an actuator.Therefore, a tensile strength of 0.3 MPs or more is necessary as apractical value.

By changing the kind and the mixing ratio of the polymer material andthe fine conductive particles, an actuator film having the coefficientof linear thermal expansion, the electric conductivity and the tensilestrength as described above can be manufactured. In this case, thespecific gravity of the actuator varies in accordance with the type andthe mixing ratio. Since the fine carbon particles used in Embodiment 1have an extremely low bulk density, when the fine particles are mixedwith the polymer, the specific gravity of the mixed material is lessthan the specific gravity of the polymer. However, in a case where theamount of the fine particles is excessively large relative to thepolymer, a film can no more be formed. Since the specific gravity of themixed material in this instance is about 0.5, it is desirable that thespecific gravity of the mixed material be 0.5 or more. Further, sincethe object of the invention is to provide an actuator of a reducedweight, a material of a large specific gravity such as metal does notconform to the purpose of the invention. Accordingly, a material withthe specific gravity of 5 or less is practical.

By using the polymer material and the fine conductive particle materialdescribed previously and optimizing the mixing ratio, an actuator filmhaving a heat resistance of 100° C. or higher, a coefficient of linearthermal expansion of from 0.00001/K to 0.0001/K, an electricconductivity of from 0.1 to 100 siemens/cm, a specific gravity of from0.5 to 5, and a tensile strength of from 0.3 to 200 MPa can bemanufactured easily.

Physical properties of several actuator films manufactured from polymermaterials and fine conductive particles in combination are shown inTable 2 by way of example. TABLE 2 Fine Weight ratio Coefficient oflinear Electric Tensile Conductive (polymer:fine thermal expansionconductivity Specific strength Polymer material particles particle) α(×10⁻⁵/K) k(S/cm) gravity σ (MPa) Perfluorosulfonic Nickel 2:8 5 26 5 2acid-copolymer (diameter: 1 μm) Perfluorosulfonic Carbon 4:6 5 0.7 0.9 4acid-copolymer (diameter: 5 μm) Polymethyl Carbon 3:7 4 1 0.6 50methacrylate (diameter 40 nm)

Further, while the description has been made for FIG. 1 and FIG. 2 byusing an actuator material that expands by electric supply, an actuatorthat contracts by electric supply can be manufactured by using amaterial having a negative thermal expansion coefficient such aspolyparaphenylene benzobisoxazole as the polymer material 2.

A method of manufacturing the actuator film of Embodiment 1 is to bedescribed with reference to FIGS. 4A to 4D. FIGS. 4A to 4D areconceptional views showing a step for the method of manufacturing theactuator film of Embodiment 1.

At first, fine conductive particles 13 are mixed at an optional ratio toa solution in which a polymer 11 is dispersed in a solvent 12 (liquidpolymer dispersion) and stirred to prepare a fine particle-mixedsolution 14 (FIG. 4A). In Embodiment 1, the liquid polymer dispersion isa solution formed by dispersing a perfluorosulfonic acid-copolymer by 5%to a mixed solvent of water and alcohol (mixing ratio 1:1), or a mixedsolution of the solution described above and dimethyl formamide. Finecarbon particles with a diameter of about 40 nm are used for the fineconductive particles 13.

Then, the thus prepared fine particle-mixed solution 14 is coated on asubstrate 15 and dried at a high temperature of 70° C., to prepare amixed film 16 of the polymer and the fine conductive particles(thickness: 120 μm) (FIG. 4B). In Embodiment 1, a glass substrate isused for the substrate 15. Further, in Embodiment 1, while the dryingtemperature is set at 70° C., the drying temperature region can be fromroom temperature to 180° C. As the coating method, any of a cast method,a spin coating method, or a spray coating method can be used.

Then, the dried mixed film 16 of the polymer and the fine conductiveparticles is dipped in purified water 17 in a state of being depositedto the substrate 15 as it is. Then, the mixed film 16 of the polymer andthe fine conductive particles swells and peels from the substrate 15(FIG. 4C).

Finally, the peeled mixed film 16 of the polymer and the fine conductiveparticles is scooped and unnecessary portions are mechanically cut outto provide an arranged optional shape, thereby completing an actuatorfilm 1 (FIG. 4D).

In the shaping treatment in FIG. 4D, while the shape was arranged bymechanical cutting, the shape may also be arranged by dry etching usingan oxygen gas, etc. Further, while the shape of the actuator film isarranged after peeling from the substrate 15, it may be arranged alsobefore peeling. Further, as shown in FIG. 5, an actuator of a requiredshape can be obtained also by forming an indent 22 corresponding to thenecessary shape of the actuator film 1 in the substrate 21, casting amixed solution of the fine particles into the indent 22 and then dryingand peeling the same.

Further, while the liquid dispersion of the polymer in which the polymer11 is dispersed in the solvent 12 is used in FIG. 4, it can also beprepared, instead, by mixing and kneading the fine conductive particlesto the polymer in the molten state. A heat compression or melt extrusionmethod used for usual resin fabrication can be adopted for molding.

According to Embodiment 1, an actuator of an optional film shape capableof stable expanding and contracting operation by the application ofvoltage in atmospheric air can be manufactured easily.

EMBODIMENT 2

In Embodiment 2, an actuator module structure using the actuator of theinvention and an actuator matrix utilizing the same are to be describedwith reference to FIGS. 6A to 8B. FIGS. 6A and 6B are cross sectionalviews showing the concept of the actuator module structure of theinvention in which FIG. 6A is a cross sectional view of an actuatormodule in a state before application of a voltage and FIG. 6B is a crosssectional view of the actuator module in a state upon application of thevoltage. In an actuator module 60, a stretchable member 64 is disposedin an open plane of an elongate box-shaped container 65, and electrodes62, 63 are buried in the bottom of the container 65. An actuator film 61turned back at the central portion thereof is disposed inside thecontainer 65, the turned back portion is joined to the lower surface ofthe stretchable member 64 at the upper surface of the container 65, andboth ends of the actuator film 61 are joined with the respectiveelectrodes 62, 63. A pin 66 is joined to the rear face of thestretchable member 64 to which the actuator film 61 is joined such thatit overlaps the actuator film 61. The actuator film 61 is adjusted inlength so that it may always undergo tension by the stretchable member64. One or more of heat dissipation holes 67 are punctured in thecontainer 65. Instead of the heat dissipation hole, a structure may beadopted of attaching a Peltier device on the lateral surface inside thecontainer 65 to cool the actuator film 61.

When a voltage is applied between the electrodes 62 and 63 of theactuator module 60, the actuator film 61 undergoing the tension from thestretchable member 64 can expand to move the pin 66 upward (FIG. 6B).Further, the pin 66 is moved downward again by lowering the value of theapplied voltage or turning off the switch 5. In this way, the pin 66 canbe moved vertically by the voltage signal.

One of methods of magnifying the movement of a expanding actuator ofsmall strain uses a V-shaped structure. The V-shaped structure means astructure in which both ends of the expanding actuator are fixed and aload is applied to the central portion of the actuator perpendicularlythereto. Both ends of the actuator are fixed to a container such thatthe expanding actuator is straightened in a contracted state. Then, whenthe actuator is extended in this state, the central portion isdistorted. When the distortion is taken out as a displacement in thedirection perpendicular to the actuator by a load applied to the centralportion, it is possible to obtain a value much greater than thedisplacement obtained by the expansion and contraction in the extendingdirection of the actuator at the open end of the actuator.

FIGS. 7A to 7C are conceptional views showing the state of an actuatormodule structure utilizing the V-shaped structure. FIG. 7A is an upperperspective view showing the outer profile of an actuator module usingthe V-structure, FIG. 7B is a cross sectional view of the actuatormodule showing the state in which the pin is lowered with no applicationof a voltage and FIG. 7C is a cross sectional view of the actuatormodule showing the state in which the pin is moved upward by extendingthe actuator film with application of the voltage to the actuatormodule.

An actuator module 70 has a configuration of joining a bottom container74 and a lid 76, in which a pin 78 moves vertically through an opening75 at the central portion of the lid 76. An actuator film 71 is disposedin the upper surface of the bottom container 74, and both ends of theactuator film 71 are connected with respective electrodes 72, 73 buriedin the side wall of the bottom container 74. A spring 77 for exerting aforce pushing the actuator film 71 upward is disposed to the centralportion of the actuator film 71 between the film and the bottom of thebottom container 74. A pin 78 is disposed at a position opposite to thespring 77 in contact with the actuator film 71. Further, although notillustrated, one or a plurality of heat dissipating holes are perforatedin the bottom container 74 and the lid 76. Further, instead of the heatdissipating hole, a structure may be adopted attaching a Peltier deviceat the bottom of the container 74 for cooling the actuator film 71.

The length of the pin 78 is adjusted such that the upper surface of thepin 78 is below the surface of the lid 76 before application of avoltage to the electrodes 72, 73, that is, before extension of theactuator film (FIG. 7B). When a voltage is applied to the electrodes 72,73, the actuator film 71 is extended, the pin 78 is moved upward by thespring 77 and thus the upper surface of the pin 78 appears above thesurface of the lid 76. Further, when the application of the voltage isinterrupted or the value of the applied voltage is lowered, the pin 78is lowered again. As described above, the pin 78 can be moved verticallydepending on the voltage signal.

In the actuator module shown in FIG. 7, in a case of using the actuatorfilm 71 of with a length of 1 cm and expanding and contracting the filmat 2%, the pin 78 can be vertically moved by 1 mm.

The actuator module shown in FIG. 7 has a feature in that not only alarge displacement can be taken out but also the actuator matrix can beeasily formed by joining the respective wall surfaces of the bottomcontainers 74 together. Further, the actuator matrix composed of theactuator modules shown in FIG. 7 has an advantage that the displacementis large, as well as the thickness thereof can be decreased.

FIGS. 8A and 8B are conceptional upper plan views showing an actuatormatrix using the actuator module shown in FIGS. 7A to 7C. FIG. 8A showsan example of a one-dimensional actuator matrix in which actuator modulecontainers 74 are arranged such that its longitudinal lateral surfacesare parallel to one another and its pins 78 are aligned with oneanother. FIG. 8B shows an example of a two-dimensional actuator matrixin which actuator module pins 78 are arranged in a two-dimensionalmanner such that its longitudinal lateral surfaces are parallel to oneanother and are slightly displaced with one another.

EMBODIMENT 3

Embodiment 3 proposes a Braille display device as one of portable hapticdevices as an application example of the actuator module shown inEmbodiment 2, as well as a Braille display system using the same, whichis to be described with reference to FIGS. 9A, 9B, 10A and 10B.

A Braille cell is expressed as a unit in which protrusions each having aheight of about 0.4 mm are arranged about 2.2 mm apart to constitute a3×2 dot matrix. The Braille display device of Embodiment 3 is a devicein which six pins are arranged as a 3×2 matrix and an optional pin canbe moved vertically at 0.4 mm stroke in response to electric signals.

A most simple Braille display device using the actuator module accordingto the invention is an actuator matrix using the actuator module 60described in FIG. 6 for Embodiment 2 and arranging them in 3×2arrangement. FIG. 9A is a conceptional view in which Braille displaydevice 90 having actuator modules 60 arranged in 3×2 is viewed fromabove obliquely, and FIG. 9(B) is a conceptional view of a Brailledisplay system 91 using the Braille display devices 90.

The actuator module 60 is configured as described below to meet thespecifications of Braille.

(1) To arrange the pins about 2.2 mm apart, the cross section of theactuator module 60 as viewed from above is sized 2.2 mm×2.2 mm.

(2) Since it is necessary to move the pin vertically by 0.4 mm, thelength of the actuator film 61 before turn back is set to about 40 mmand a voltage is applied such that the strain is 2%.

A Braille display system 91 includes a Braille display terminal 92having a plurality of the Braille display devices 90, a control device93 such as a central processing unit (CPU), and a driving signalgenerating device 94 connected to the control device. The driving signalgeneration device 94 is controlled by the instruction from the controldevice 93 to apply a voltage to necessary actuator modules. A sentencedisplayed by Braille can be read in this state by touching over theupper surface of the Braille display terminal 92. Since the Brailledisplay device 90 using the invention is small in size and light inweight, also a small and light Braille display terminal can be attained.In FIG. 9, heat dissipating holes are not illustrated.

FIG. 10A is a conceptional upper plan view showing the state of aBraille display device 100 in which the actuator modules 70 describedfor Embodiment 2 in FIG. 7 are arranged by 3×2, and FIG. 10B is aconceptional view of a Braille display system 101 using the Brailledisplay device 100. To meet the specifications of the Braille, theactuator module is configured as below.

(1) To arrange the pins about 2.2 mm apart, the width of the actuatormodule viewed from above is set to 0.98 mm.

(2) Since it is necessary to vertically move the pin by 0.4 mm, thelength of the actuator film 71 is set to about 4 mm.

By arranging the actuator modules by the number of 6 in the longitudinaldirection of the actuator module so as to be alternately displaced by1.96 mm each, a Braille display device in which Braille is displayed bythe application of voltage to optional actuator modules can be obtained.

The Braille display system 101 is the same as the Braille display system91 except for providing a Braille display terminal 102 having aplurality of the Braille display devices 100. Since the Braille displaydevice 100 using the actuator module 70 is further reduced in thicknessand in weight compared with the Braille display device 90 using theactuator module 60, the Braille display terminal 102 reduced inthickness and in weight can also be obtained.

EMBODIMENT 4

In Embodiment 4, an actuator module in which the expanding andcontracting operation of the actuator film described for Embodiment 1 ismodified into a bending operation is to be described with reference toFIGS. 11A and 11B.

FIG. 11A is a schematic upper perspective view of an actuator module 110in a state before application of a voltage, and FIG. 11B is aconceptional upper perspective view of an actuator module 110 in thestate of applying the voltage. An actuator module 110 has a structure inwhich an actuator film 111 formed into a U-shape is adhered to aninsulator film 112 formed into the identical shape with no displacementtherebetween and electrodes 113, 114 are fixedly attached to both endsof the actuator film 111. When a voltage is applied between theelectrodes 113 and 114, current flows to the actuator film 111 togenerate Joule heat and the film 111 expands or contracts. In this case,if the insulator film 112 uses a material having a thermal expansioncoefficient smaller than that of the actuator film 111, the bonded filmis warped due to the difference in the expansion coefficient between thesurface and the rear face of the bonded films.

In Embodiment 4, a film of 30 μm thick comprising a mixed material ofperfluorosulfonic acid-copolymer and fine carbon particles described inEmbodiment 1 is used being formed into an U-shaped outer profile of 1 cmsquare as the actuator film 111. A polyimide film of 25 μm thick is usedfor the insulator film 112 and bonded with the actuator film 111 usingan epoxy adhesive. When a voltage of 15 V is applied between theelectrode 113 and electrode 114 of the actuator module 110, the top endof the film is warped downward by about 3 mm. The displacement at thetop end of the film in this case is much greater than the displacementin the extending direction obtained by the actuator film explained forEmbodiment 1. As described above, a larger displacement can be obtainedin the bending actuator module.

EMBODIMENT 5

Embodiment 5 proposes an example of applying the bending actuator module110 explained for Embodiment 4 to a conveying device for conveying alight weight product such as paper, and an optical switching device forswitching the optical channel of an optical fiber. This is to beexplained with reference to FIG. 12 to FIG. 14. Further, an opticalswitching device using the actuator module of the V-structure explainedfor Embodiment 2 is also explained with reference to FIG. 15.

FIG. 12A is a schematic plan view, as shown from overhead, for the stateof a conveying device 120 utilizing a plurality of the bending actuatormodules 110 explained for Embodiment 4 and a conveying system alsoincluding a control circuit for operating the conveying device 120. FIG.12B is a perspective view of the conveying device 120. The conveyingsystem comprises the conveying device 120, a signal switching device121, and a power control device 122. The conveying device 120 includes asubstrate 123, bending actuator modules 110, metal electrodes 124, awiring pattern 125, and voltage input terminals 126 a, 126 b, 126 c, and126 d. The bending actuator modules 110 explained for Embodiment 4 eachformed to an identical size are arranged in a 4×4 matrix on thesubstrate 123. The bending actuator modules 110 are arranged such thatthe direction of the U-shape is identical on every columns and thedirection of the U-shape is inverted between adjacent rows to eachother. Both ends of the actuator film surface of the bending actuatormodule 110 are electrically connected with metal electrodes 124 drawn onthe substrate 123. Further, they are secured at the ends connected withthe metal electrode 124 of the bending actuator module 110 to the uppersurface of the substrate 123, and the surface of the insulator film 112is on the upper surface of the substrate 123. The bending actuatormodules 110 are eclectically connected in parallel on every columns bythe metal electrode 124 and the wiring pattern 125. The bending actuatormodules 110 are connected at terminals on one side with the voltageinput terminals 126 a, 126 b, 126 c, and 126 d on every columns and atthe terminals on the other side with the common ground terminals 129.The voltage input terminals 126 a, 126 b, 126 c, and 126 d areconnected, respectively, by way of a signal switching device 121comprising switches 127 a, 127 b, 127 c, and 127 d to the power controldevice 122.

In the arrangement shown in FIG. 12, when the actuator module 110 isbent, the top end displaces upward (in the direction apart from theupper surface of the substrate 123) opposite to that in FIG. 11B. Thatis, since it displaces in the direction z and in the direction x in thedrawing, it conveys a material in the direction x. The conveying methodof the material is to be described with reference to FIGS. 13A to 13E. Adoted chain drawn through FIGS. 13A to 13E indicates the end face in theconveying direction where the conveyed product 130 situates initially.

FIG. 13A shows a state in which none of the actuator columns 128 a, 128b, 128 c, and 128 d arranged on the substrate 123 has any electricsupply. A product to be conveyed 130 is placed over the plurality ofactuator columns. FIG. 13B shows a state in which the switches 127 b and127 d are turned on for electric supply to the actuator column 128 b andthe actuator column 128 d. The actuator columns 128 b and 128 d underelectric supply are bent upward and the product 130 is raised by theactuator column 128 b and the actuator column 128 d. In this case, sincethe direction of the displacement at the top end of the actuator is inthe direction z and the direction x, the product to be conveyed 130 israised (displacement in the direction z) and moved by X₁ in thedirection x. FIG. 13C shows a state in which the switch 127 a and 127 care turned on from the state in FIG. 13B, to conduct electric supplyalso to the actuator column 128 a and the actuator column 128 c to bendthem upward like the actuator column 128 b and the actuator column 128d. In this case, the product 130 is raised by all the actuator columns128 a, 128 b, 128 c, and 128 d. Subsequently, as shown in FIG. 13D,electric supply to the actuator column 128 b and the actuator column 128d are interrupted and the product 130 is supported by the actuatorcolumn 128 a and the actuator column 128 c. That is, the product 130initially raised by the actuator column 128 b and the actuator column128 d is supported by the actuator column 128 a and the actuator column128 c. As shown in FIG. 12E, electric supply to the actuator column 128a and the actuator column 128 c is interrupted subsequently. FIG. 12Eshows a state just after interruption of electric supply. Bending of theactuator column 128 a and the actuator column 128 c is decreased in thisstate, and the top end of the actuator displaces in the direction −z andin the direction x. In accordance with the displacement at the top end,the conveyed product 130 lowers to the upper surface of the substrate123 and also moves in the direction x. As a result, the end face of theproduct 130 moves from the initial position shown in FIG. 13A in thedirection x by X₂. When the conveying system of Embodiment 5 is used,the product 130 can be conveyed in the direction x in the course shownin FIGS. 13A to 13E and repetition of the process will provide a largeconveying distance. Since the bending actuator module according to theinvention can be reduced in weight and reduced in size, a conveyingdevice with a small occupying area and reduced in weight can bemanufactured easily.

The conveying device described in FIG. 13 is useful for the conveyanceof light weight products such as paper and, accordingly, applicable alsoto the conveyance of banknotes in ATM, conveyance of paper in printers,etc. In this case, since conveyance is not restricted only to thehorizontal conveyance, in a case where two conveying devices shown inFIG. 13 are arranged so as to oppose on both sides of the conveyingroute to convey paper under pressing, vertical conveyance is alsopossible. In this case, it is necessary to displace the timing ofvoltage application. such that when one of them changes from FIG. 13A toFIG. 13B, the other of them is in the state from FIG. 13D to FIG. 13E.This means that it can also cope with the conveyance along a curvedsurface so long as its radius of curvature can be sufficiently large.

FIG. 14A and FIG. 14B are conceptional views showing an opticalswitching device for switching the optical channel of the optical fiberas another application embodiment of the bending actuator module shownin Embodiment 4. FIG. 14A shows, in cross section, a state of theoptical switching device in which a voltage is not applied to thebending actuator module 110. FIG. 14B is a view showing in a crosssection, a state of the optical switching device in a case where thevoltage is applied to the bending actuator module 110, to bend theactuator thereby switching the optical channel.

An optical switching device 140 shown in Embodiment 5 includes acontainer 144 in which a system of light input optical fiber 141, twosystems of output optical fibers 142 a and 142 b, and paired electrodes143 for supplying a voltage to the actuator module are buried. Theoptical switching device 140 further includes an input light condensinglens 145, collimate lenses 146 a, 146 b, and a bending actuator module110 described for Embodiment 4 joined with a minute mirror 147 containedin the container 144. A power control device 148 for supplying a voltageto the actuator module is connected with the paired electrodes 143 ofthe optical switching device 140. The bending actuator module 110 isfixed at the electrode portions on both ends to the container 144 andelectrically connected with the electrodes 143. The minute mirror 147 isfixed to the end of the bending actuator module 110 on the side oppositeto the electrode and changes the position and the angle in accordancewith the bending of the actuator. Inside the container 144, the opticalfiber 141 for light input, the lens 145 for condensing the incidentlight, the lens 146 a for introducing the incident light by collimationto the light output optical fiber 142 a, and the light output opticalfiber 142 a are arranged on a straight line. Further, the lens 146 b andthe light output optical fiber 142 b for introducing the light reflectedon the mirror 147 fixed at the top end of the bending actuator module110 into the optical fiber 142 b are arranged on a straight line.

As shown in FIG. 14A, the actuator is in a linear. state beforeapplication of a voltage to the bending actuator module 110 and a lightsignal incident from the optical fiber 141 is introduced by way oflenses 145, 146 a to an optical fiber 142 a. That is, the optical signalis outputted from the optical fiber 142 a. As shown in FIG. 14B, when avoltage is applied from the power control device 148 to the bendingactuator module 110, the bending actuator module 110 is bent and themirror 147 is inserted to the optical channel between the lenses 145 and146 a, and the light incident from the optical fiber 141 is reflected onthe mirror 147 and introduced by way of the lens 146 b to the opticalfiber 142 b. That is, the light signal is outputted from the opticalfiber 142 b. Since it is necessary that the angle of the mirror 147 isprecise for introducing the light efficiently to the optical fiber 142b, a mechanism may be provided for fixing a small electromagnet to anappropriate portion of a support fixed to a wall surface inside thecontainer 144, and fixing a minute soft magnetics (iron, silicon steal,etc.) to the mirror. Thus, the small soft magnetics fixed to the mirrorare attracted to the electromagnet after movement thereof to thevicinity of a desired position, thereby enabling precise positioning. Ina case of returning the position of the mirror, the voltage applied sofar to the bending actuator module 110 is interrupted and the switch forthe electromagnet is also turned off to release the same from theattraction state. Further, a member such as a stopper may be providedsuch that the bending actuator module 110 does not bend over apredetermined angle.

As described above, by the use of the optical switching device 140 ofEmbodiment 5, the light incident from the optical fiber 141 can beswitched from the optical 142 a to the optical fiber 142 b. Since thebending actuator module of the invention can be miniaturized, an opticalswitch reduced in size, capable of being integrated and driven at a lowvoltage can be manufactured easily.

FIG. 15 is a conceptional view showing an optical switching device 150for switching the optical channel of an optical fiber as otherembodiment of applying the actuator module of the V-structure shown inEmbodiment 2. FIG. 15A is a cross sectional view showing an opticalswitching device in a state where a voltage is not applied to theV-shaped actuator module 151. FIG. 15B is a cross sectional view showingthe optical switching device in a state of applying the voltage on theV-shaped actuator module to distort the actuator and switch the opticalchannel. The optical switching device 150 is identical with the opticalswitching device 140 described in FIGS. 14A and 14B except for theportion of the actuator module provided with a mirror 147. The actuatormodule 151 included in the optical switching device 150 is fixed at bothends to paired electrodes 143 and the mirror tilted at an angle of 45°is attached to the central portion. In a state where a voltage is notapplied to the actuator module 151, an optical signal input from theoptical fiber 141 is reflected on the mirror 147 and output to anoptical fiber 142 b (FIG. 15A). When the voltage is applied to theactuator module 151, the actuator module 151 is extended. However, sincethe both ends of the actuator module 151 are fixed, the elongation forthe change of the entire length thereof appears as a distortion in thevertical distortion. That is, the actuator module 151 is distorted andthe mirror 147 attached to the central portion thereof moves downward bygravitational force. When the mirror 147 moves downward, the opticalsignal input from the optical fiber 141 is output straight to theoptical fiber 142 a. Thus, when the optical switching device 150 ofEmbodiment 5 is used, the light incident from the optical fiber 141 canbe switched from the optical fiber 142 b to the optical fiber 142 a.

EMBODIMENT 6

In Embodiment 6, a medical tube utilizing the bending actuator moduledescribed for Embodiment 4 and the actuator film described forEmbodiment 1 is to be described with reference to FIG. 16 and FIG. 17.

FIG. 16A is a schematic view for a longitudinal cross sectionalstructure of a flexible tube 160 such as a catheter, etc. as a medicaltube. FIG. 16B is a schematic view for a cross sectional structure alongthe direction of an arrow at X-X′ in FIG. 16A. FIG. 16C is a schematicview for a cross sectional structure showing a state of bending a bentportion 161 in the flexible tube 160. FIG. 16D is a schematic view for amedical catheter system using the flexible tube 160.

As shown in FIG. 16A, the flexible tube 160 comprises a hollow tube 162disposed axially centrally, four actuator units 163 disposed to theperipheral surface of the tube 162, and a cover 164 covering them. Thetop end of the flexible tube 160 is formed as a bent portion 161bendable in an optional direction by external operation.

A hollow portion of the tube 162 is used for observation or treatment.Further, the tube is made of a soft and flexible and elastic materialsuch as silicon rubber or polyurethane and can be bent freely by anexternal force. The cover 164 covers the tube 162 and the four actuatorunits 163 and is provided with an opening 165 at the top end.

Each of the actuator units 163 comprises a plurality of bending actuatormodules 110 as described in Embodiment 4 which are connected linearly inthe axial direction of the tube 162. The bending actuator modules 110are fixed on both ends thereof, that is, at the end having the electrode166 and at the end on the side opposite to the electrode 166 to theouter peripheral surface of the tube 162. In this case, the actuatorfilm 111 formed into a U-shape and bonded with the insulator film 112 isfixed, in a slightly distorted state as shown in FIG. 16A when a voltageis not applied. Further, the bending actuator module 110 is fixed whileselecting the surface thereof such that the distortion is increased uponapplication of the voltage. The bending actuator module 110 is joinedwith the electrode 166 disposed to the outer surface of the tube 162 andconnected by way of a soft and flexible lead wire 167 joined therewithto a power control device 168 for applying a voltage to the bendingactuator module.

As shown in FIG. 16B, the actuator units 163, i.e., four actuators units163 a to 163 d are disposed along the outer periphery of the tube 162 atthe bend portion 161. As shown in FIG. 11, since the electrodes 166 aredisposed on both ends of the U-shaped actuator film, they are indicatedhere as 163 a ₁, 163 a ₂, 163 b ₁, . . . . The lead wire 167 is notillustrated in FIG. 16B since this complicates the drawing.

For bending of the bend portion 161 of the flexible tube 160 inEmbodiment 6, the actuator units 163 attached to the bend portion 161are expanded or contracted. That is, when the actuator unit 163 a iscontracted and the actuator unit 163 c disposed to the surface oppositeto the actuator unit 163 a is expanded, the bend portion 161 is bentsuch that the actuator unit 163 a is in the inner side. The bend portion161 can be bent freely in all directions if the actuator units 163 areattached at three or more positions along the outer periphery of thetube 162. FIGS. 16A and 16B show a case of providing the actuator unitsat 4 positions and, in this example, when an identical voltage isapplied simultaneously to the actuator units 163 a and 163 b, the bendportion 161 can be distorted at an angle of 45° rightward in FIG. 16B.

To provide such bending, it is necessary that the displacement of theactuator unit be large. For this purpose, in the flexible tube 160 ofEmbodiment 6, a plurality of bending actuator modules 110 having largedisplacement and arranged linearly are used for the actuator unit 163.The bending actuator module 110 is bent upon application of a voltageand is in a linear form when the voltage is not applied. The change ofthe distance between both ends of the bending actuator modules alongwith the bending is much larger compared with the change of the distancebetween both ends of the actuator film when the actuator film describedin Embodiment 1 is expanded and contracted by the application of anidentical voltage. When the actuator unit 163 is constituted utilizingthem, the displacement of the actuator unit 163 is increased.

In a case of forming the flexible tube 160 in a straight form as in FIG.16A, the position of securing the bending actuator module 110 iscontrolled such that the bending actuator module 110 is in a slightlybent state. Alternatively, four actuator units may be fixed such thatthey are in a planer state and an identical voltage may be applied toeach of them to attain a state where the bending actuator module 110 isslightly bent. This makes the length for each of the actuator units 163identical and each of the bending actuator modules 110 does not undergothe tension from the tube 162 and the flexible tube 160 can be kept in alinear state.

As shown in FIG. 16C, when a high voltage is applied from the powercontrol device 168 to the actuator unit 163 a in the flexible tube 160to greatly contract the actuator unit 163 a and the bend portion 161 isbent without applying the voltage to the actuator unit 163 c, the bendportion 161 is bent upward. The bending direction and the angle ofbending of the flexible tube 160 can be controlled by applying a signalfor designating the actuator unit to which the voltage is applied andthe magnitude of the voltage to the power control device 168.

FIG. 16D is a schematic view for a medical catheter system using theflexible tube 160. The system includes a flexible tube 160, a powercontrol device 168, and a bending operation device 169. The flexibletube 160 is connected electrically with the power control device 168.The power control device 168 is connected with the bending operationdevice 169 and applies a voltage to the actuator unit in the flexibletube 160 in accordance with the operation of the bending operationdevice 169 for designating the bending direction and the bending angleof the flexible tube 160 to thereby bend the bend portion 161 at the topend of the flexible tube 160. In this way, the flexible tube can be usedas an active catheter by operating the same close at hand and bending itfreely.

Then, another embodiment of the medical tube utilizing the actuator ofthe invention is to be described with reference to FIGS. 17A and 17B.FIG. 17A is a schematic view for the longitudinal cross sectionalstructure of a flexible tube 170 for a catheter, etc. as a medical tube.FIG. 17B is a schematic view of a cross sectional structure along thedirection of an arrow at position X-X′ shown in FIG. 17A. The flexibletube 170, like the flexible tube 160 described for FIG. 16, includes ahollow tube 172 disposed in the central portion in the axial directionused for observation, treatment, etc., four actuator units 173 a to 173d arranged along the peripheral surface of the tube 172, and a cover 174covering them. An opening 175 is provided to the top end of the flexibletube 170, and the top end of the flexible tube 170 constitutes a bendportion 171 bendable in the optional direction by the externaloperation.

The tube 172 comprises a base tube 176 made of a soft and flexiblematerial such as silicon rubber or polyurethane, and a bend tube 177connected at the top end thereof. The bend tube 177 is made of amaterial more flexible than the base tube 176 and can be bent freely byan external force easily.

The flexible tube 170 and the flexible tube 160 are different each othermainly with respect to the actuator unit. In the flexible tube 160, thedisplacement of the actuator unit 163 is increased by utilizing thebending actuator module whereas in the flexible tube 170, an actuatorunit 173 utilizing the actuator film described in Embodiment 1 is usedinstead of the bending actuator module. However, the actuator filmdescribed in Embodiment 1 has a smaller strain, i.e., a less ratio ofthe displacement of the film relative to the entire length of the film.Accordingly, the amount of displacement is increased by arranging theactuator units 173 along the axial direction of the flexible tube 170thereby increasing the entire length.

The actuator units 173 a to 173 d are bounded by the guides 178 a to 178d attached to the outside of the tube 172. Then, the actuator units 173are movable in the axial direction of the tube 172 but are restrictedfrom movement in the radial direction. The distance between each of theguides 178 a to 178 d is made shorter at the position for the bend tube177 than that at the position for the base tube 176. Further, both endsof the actuator unit 173 are fixed to both ends of the tube 172. Avoltage from the power control device 168 can be applied by way of asoft and flexible lead wire 167 to the both ends of each actuator unit173. As described above for Embodiment 1, the actuator unit 173 appliedwith the voltage is contracted. Accordingly, the bend tube 177 is bentsuch that the contracted actuator unit 173 is on the inner side. Sincethe plurality of actuator units 173 are provided (by the number of fourin FIGS. 17A and 17B) along the peripheral surface of the bend tube 177,when an actuator unit 173 to be applied with the voltage is determinedin accordance with the direction desired to bend the flexible tube 170and the voltage is applied thereto, the bend portion 171 of the flexibletube 170 can be bent in all directions freely as in the case of theflexible tube 160. Accordingly, as described for FIG. 16D, the bendportion 171 of the flexible tube 170 can be bent freely in response tothe electric signals.

In FIG. 17, while the electrodes are attached to both ends of theactuator film 1, when the resistance of the actuator film is high, nosufficient operation can be expected unless the voltage of the powersource is high. Accordingly, the power source voltage can be kept low byattaching a plurality of electrodes in the midway of the actuator filmto operate the same in parallel.

Since the actuator module according to the invention is reduced inweight and miniaturized in size, a medical tube small in size andreduced in weight can be manufactured easily by utilizing the same.

Reference numerals used in the drawings of this specification are listedas follows:

1 . . . actuator film, 2 . . . polymer material, 3 . . . fine conductiveparticles, 4 . . . power source, 5 . . . switch, 6 . . . electrode, 7 .. . electrode, 8 . . . load, 10 . . . actuator material, 11 . . .polymer, 12 . . . solvent, 13 . . . fine conductive particles, 14 . . .mixed solution of polymer and fine conductive particles, 15 . . .substrate, 16 . . . film comprising a mixture of polymer and theconductive particles, 17 . . . purified water, 21 . . . substrate, 22 .. . mold, 60 . . . actuator module, 61 . . . actuator film, 62 . . .electrode, 63 . . . electrode, 64 . . . stretching member, 65 . . .container, 66 . . . pin, 70 . . . actuator module, 71 . . . actuatorfilm, 72 . . . electrode, 73 . . . electrode, 74 . . . container, 75 . .. hole, 76 . . . lid, 77 . . . spring, 78 . . . pin, 90 . . . Brailledisplay device, 91 . . . Braille display system, 92 . . . Brailledisplay terminal, 93 . . . control and instruction device, 94 . . .driving signal generation device, 100 . . . Braille display device, 101. . . Braille display system, 102 . . . Braille display terminal, 110 .. . bending actuator module, 111 . . . actuator film, 112 . . .insulator film, 113 . . . electrode, 114 . . . electrode, 120 . . .conveying device, 121 . . . signals switching device, 122 . . . powercontrol device, 123 . . . substrate, 124 . . . metal electrode, 125 . .. wiring pattern, 126 a-d . . . voltage input terminal, 127 a-d . . .switch, 129 . . . ground terminal, 130 . . . product to be conveyed, 140. . . optical switching device, 141 . . . light inputting optical fiber,142 a . . . light outputting optical fiber, 142 b . . . light outputtingoptical fiber, 143 . . . paired electrode, 144 . . . container, 145 . .. input light condensing lens, 146 a . . . collimate lens, 146 b . . .collimate lens, 147 . . . mirror, 148 . . . power control device, 150 .. . optical switch, 151 . . . actuator module, 160 . . . flexible tube,161 . . . bend portion, 162 . . . tube, 163 actuator unit, 164 . . .cover, 165 . . . hole, 166 . . . electrode, 167 . . . lead wire, 168power control device, 169 . . . bend portion operating device, 170 . . .flexible tube, 171 . . . bend portion, 172 . . . tube, 173 actuatorunit, 174 . . . cover, 175 . . . hole, 176 . . . base tube, 177 . . .bend tube, 178 . . . guide

1. An actuator comprising: a molding product of a material comprising amixture of fine conductive particles and a polymer material, thematerial expanding or contracting by electric supply; and at least twoelectrodes for electric supply disposed on both side portions of themolding product which expands or contracts.
 2. An actuator according toclaim 1, wherein the molding product deforms by thermal expansion orthermal contraction accompanying heat generation by Joule heat caused byan electric current flowing between the electrodes formed at the moldingproduct.
 3. An actuator according to claim 1, wherein an amount ofdeformation of the actuator is controlled by adjusting a voltage appliedbetween the electrodes.
 4. An actuator according to claim 1, wherein theactuator performs a function of the actuator by use of a load that theactuator undergoes.
 5. An actuator according to claim 1, wherein thematerial has a coefficient of a linear thermal expansion of 0.00001 to0.001/K within a temperature range from 100° C. to 200° C., an electricconductivity of from 0.1 to 1000 S/cm within a temperature range from100° C. to 200° C., and a specific gravity of from 0.5 to 5 within atemperature range from 100° C. to 200° C.
 6. An actuator according toclaim 1, wherein the material has a tensile strength of from 0.3 MPa to200 MPa within a temperature range from 100° C. to 200° C.
 7. Anactuator according to claim 1, wherein the material has a coefficient oflinear thermal expansion of from 0.00005 to 0.0002/K within atemperature range from 100° C. to 200° C.
 8. An actuator according toclaim 1, wherein the material has an electric conductivity of from 0.1to 100 S/cm within a temperature range from 100° C. to 200° C.
 9. Anactuator according to claim 1, wherein the material has a specificgravity of from 0.5 to 5 within a temperature range from 100° C. to 200°C.
 10. An actuator according to claim 1, wherein the material has atensile strength of from 1 MPa to 100 MPa within a temperature rangefrom 100° C. to 200° C.
 11. An actuator according to claim 1, whereinthe current upon electric supply to the molding product is restrictedsuch that the temperature of the molding product can be kept to theglass transition temperature of the material or lower.
 12. An actuatoraccording to claim 1, wherein the fine conductive particles comprise afine conductor of fine carbon particles, fine platinum particles, finegold particles, fine silver particles, fine nickel particles, finecopper particles, carbon nanotubes or a mixture thereof.
 13. An actuatoraccording to claim 1, wherein the polymer is perfluorosulfonicacid-copolymer, acrylonitrile-butadiene-styrene resin, polymethylmethacrylate such as acrylic resin, polyethylene terephthalate,polyamide, polyoxymethylene, polytetrafluoroethylene, polystyrene,polycarbonate, polyalkenes such as polycyclohexylethylene, polyacrylicacid, or polymethacrylic acid.
 14. An actuator module comprising: anactuator film of a material comprising a mixture of fine conductiveparticles and a polymer material, the material expanding or contractingby electric supply; and at least two electrodes for electric supplydisposed on both side portions of the actuator film which expands orcontracts; wherein the actuator film and the two electrodes are housedin a predetermined container.
 15. An actuator module according to claim14, wherein the two electrodes of the actuator film are respectivelyfixed to opposing inner surfaces of the container, and a load is coupledto a central portion of the actuator film to render the actuator filmalways put under tension.
 16. An actuator module: comprising asubstrate; a multi-layered film in which an actuator film of a materialcomprising a mixture of fine conductive particles and a polymer materialand expanding or contracting by electric supply is bonded to a filmcomprising a material having a thermal expansion coefficient smallerthan that of the actuator film; and at least two electrodes for electricsupply disposed on at both side portions of the actuator film whichexpands or contracts; where the multi-layered film has one end fixed tothe substrate.
 17. An actuator module according to claim 16, wherein arow of multi-layered films in which the multi-layered films are formedeach in a predetermined shape, a plurality of the multi-layered filmsare arranged parallel to each other, and the same ends of themulti-layered films arranged parallel to each other are fixed on thesubstrate, and another row of multi-layered films has the. sameconfiguration as that of the row of the multi-layered films describedabove, and is configured such that the same ends of multi-layered filmsarranged in a direction opposite to that of the row of the multi-layeredfilms described above are fixed on the substrate, are arranged parallelto each other.
 18. An actuator module according to claim 17 wherein aplurality of the paired rows of the multi-layered films are arrangedparallel to each other, and a voltage is applied alternately to theactuator films of the respective rows of the multi-layered films fixedat the same ends thereof onto the substrate.
 19. An actuator modulecomprising: a hollow tube with a highly flexible top end; three actuatorfilms of a material comprising a mixture of fine conductive particlesand a polymer material, fixed on an outer surface of the tube in anaxial direction of the tube and expanding or contracting by electricsupply; at least two electrodes for electric supply disposed on bothside portions of the actuator film which expands or contracts; leadwires connected with the electrodes and extending along the outersurface of the tube; and an outer cylinder covering the hollow tube, theactuator film, an electrode, and the lead wire.
 20. An actuator moduleaccording to claim 19, wherein the top end of the hollow tube is moreflexible than a central portion of the tube.